57 Chevy's etc.. did not come with 427 engines etc. so if you bought one thats custom it wouldn't matter.
E bodies are pulling Big $$, so to ask the differences is a doubles edge sword. like fender tags. keep it secret cuts down on fraud.
someone paying big dollars for a high dollar e body can get an expert. sure worth it.
Even Nazi SS stuff has alot a counterfeits. WHY? $$